Inhalation is a very old method of drug delivery. In the twentieth century it became a mainstay of respiratory care and was known as aerosol therapy. Use of inhaled epinephrine for relief of asthma was reported as early as 1929, in England. Dry powder inhalers have been used to administer penicillin dust to treat respiratory infections. In 1956, the first metered dosed inhaler was approved for clinical use.
The scientific basis for aerosol therapy developed relatively late, following the 1974 Sugar Loaf conference on the scientific basis of respiratory therapy. A more complete history of the development of aerosol therapy and the modern nebulizer is described in the 2004 Phillip Kitridge Memorial Lecture entitled, “The Inhalation of Drugs: Advantages and Problems by Joseph L. Row; printed in the March 2005 issue of Respiratory Care, vol. 50, no. 3.
Table 8 of the Respiratory Care article, referred to above, page 381, lists the characteristics of an ideal aerosol inhaler as follows:
TABLE 8Dose reliability and reproducibilityHigh lung-deposition efficiency (target lung deposition of100% of nominal dose)Production of the fine particles ≦5 μm diameter, withcorrespondingly low mass median diameterSimple to use and handleShort treatment timeSmall size and easy to carryMultiple-dose capabilityResistance to bacterial contaminationDurableCost-effectiveNo drug released to ambient-airEfficient (small particle size, high lung deposition) forthe specific drug being aerosolizedLiked by patients and health care personnel
Standard nebulizers typically fail to achieve a number of these characteristics because they waste medication during exhalation. Further, the particle size is often too large to reach the bottom of the lungs where the medication may be most needed. There is difficulty in estimating the dose of the drug being given to a patient and there is difficulty in reproducing that dose. There is a possibility of contamination when opening the initially sterile kit, pouring medication into the cup, and assembling the pieces for use by a patient. There is also considerable inefficiency in the medication delivery, with much of it being deposited in the throat, rather than in the lungs.
Commonly assigned U.S. Pat. No. 8,109,266, the disclosure which is hereby incorporated by reference in its entirety, discloses a nebulizer having a flow meter function that is applied to venturi type intra-oral nebulizers as disclosed in commonly assigned U.S. Pat. Nos. 7,712,466 and 7,726,306, the disclosures which are hereby incorporated by reference in their entirety. These nebulizers are horizontally configured, and in one example, include a venturi at a rainfall chamber. Further enhancements to the nebulizers are desirable.